Since
at least the time of Shakespeare, people have been talking about the Bermuda
Triangle, the area of the Atlantic between Miami, San Juan, Puerto Rico and
Bermuda, where an anomalously high number of ships and planes have reportedly
gone missing. Perhaps the most famous disappearance involves Flight 19, a World
War II Navy Avenger squadron that disappeared in the region during a routine
training mission off the coast of Florida. To this day, the five planes have
not been located, nor do people know why they disappeared. But Flight 19 and
others can all be explained by reasonable science, says Bill Dillon, a geologist
emeritus with the U.S. Geological Survey (USGS) in Woods Hole, Mass.

Five Navy Avengers similar to those pictured
here disappeared in the Bermuda Triangle on Dec. 5, 1945, during a routine training
mission. Nothing was ever found of the planes or the crew. Courtesy of the Naval
Historical Center.

This region, which is not recognized by the U.S. Coast Guard as a geographic
area of specific hazard to ships or planes, is known for wild and sudden storms,
hurricanes and water spouts, the strong and turbulent Gulf Stream, and interesting
seafloor topography, going from a gently sloping continental shelf to a deep
drop-off, Dillon says. Additionally, many recreational boats and small planes
traverse the region, so its not surprising at all that many ships
go down there, he says. But another more speculative explanation has come
into the scientific discussion lately: that giant gas bubbles could be rising
from the deep and swallowing ships whole.

In the early 1980s, geologist Richard McIver published an article in the AAPG
Explorer suggesting that methane hydrates  a crystalline solid of
methane gas and water, similar to ice (see sidebar) 
on the ocean floor could break apart and release giant methane gas bubbles that
could cause ships or airplanes to sink or explode. The article was sort of tongue-in-cheek,
Dillon says, but the explanation for the disappearances in the Bermuda Triangle
struck a chord and quickly propagated through the media. And because most geologists
might go so far as to say it is conceivable, Dillon says, the explanation has
stuck around, despite some inherent flaws.

Methane hydrate is located in great volume all over the world, mostly on continental
margins in the ocean or in permafrost in the Arctic, in places where the cold
sea or land temperatures and extensive pressures hold them stable. Mapping has
shown vast hydrate deposits off the East Coast of the United States from New
Jersey to Georgia, although few, if any, in the actual area of the Bermuda Triangle,
Dillon says.

The hydrate hypothesis for the Bermuda Triangle is that some trigger, such as
an undersea landslide, would cause hydrate deposits to break apart and release
a tremendous gas bubble. That burp would reduce the density of water
and, when it hit the sea surface under a ship, would cause the buoyancy of the
ship to decrease and thus sink, says Bruce Denardo, a physicist with the Naval
Postgraduate School in Monterey, Calif. With airplanes, possibilities include
that as the methane gas cloud rises through the air, the heat from the engines
of an airplane flying through it would cause the cloud to ignite and thus incinerate
the plane, or that the methane would replace enough oxygen in the air to cause
the engines to quit.

The sinking of ships by turning the ocean to froth is certainly physically
possible, Dillon says. But that possibility does not speak to chance or
probability, says Bill Durham, a geophysicist at Lawrence Livermore National
Laboratory in Livermore, Calif., who believes that the methane hydrates explanation
is as good as any other but wouldnt bet on it. The thing
is, when geologists say something is plausible, theyre talking about on
the geologic time scale, he says.

And indeed, submarine landslides have released large methane clouds in the past
 about 13,000 years ago, says Debbie Hutchinson, a geologist at USGS in
Woods Hole. Back then, sea level was much lower than it is now, which lowered
the pressure on hydrate deposits and may have allowed them to melt and release
gas. The high pressure exerted on the deposits in the last several thousand
years from rising sea levels acts to stabilize them.

While hypothetically I think bubbles could release and cause boats to
sink, the likelihood is so remote that it just cant explain the
disappearances in the Bermuda Triangle, Hutchinson says. To sink a ship, it
would have to be floating at just the right spot at just the right time. Furthermore,
she says, as remote a possibility as it is that one boat would encounter a bubble
and sink, the probability is even lower that such a phenomenon could cause more
than one disappearance.

Another problem with the methane hydrate explanation, Durham says, is that methane
gas released from a trap below the hydrate deposits would likely dissolve in
the ocean water before reaching the surface. And, Dillon adds, if disturbed
enough to break apart, the deposits themselves would likely float to the surface
and then very slowly release gas, not in an explosive bubble.

Beyond the geology issues, there are also physics issues, says Denardo, who
says as an educated member of the public, he just doesnt see
enough evidence to believe in the Bermuda Triangles deadly mystery. He
has performed tests on floating objects to determine the amount of bubbles needed
to sink a ship. Fluid dynamics is enormously complicated, he says, and sinking
a ship by reducing the buoyancy requires a vast amount of bubbles, especially
because the bubbles may additionally cause an upward force on the ship, making
it more difficult to sink. The ocean is much more complicated than our
laboratory experiments, Denardo says.

Finally, Hutchinson adds, it is important to note that official records of shipwrecks
and disappearances indicate no statistically higher incidence of wrecks in this
region than in other regions worldwide. Thus, perhaps no unique explanation
is necessary.

The Bermuda Triangle is a fairy tale, Dillon says. The story got
into the public mind, and its one of those things that just keeps
coming up every few years, like aliens with egg-shaped heads swooping down to
Earth to abduct people, he says. I would rather believe in aliens
with egg-shaped heads than in a gas bubble from hydrates sinking ships and planes
in the Bermuda Triangle. But of course, he adds, I dont believe
in either tale.